Chapter 6: Safe and Active

Although physical activity has many health benefits, injuries and other
adverse events do sometimes happen. The most common injuries affect the
musculoskeletal system (the bones, joints, muscles, ligaments, and tendons).
Other adverse events can also occur during activity, such as overheating and
dehydration. On rare occasions, people have heart attacks during activity.

The good news is that scientific evidence strongly shows that physical
activity is safe for almost everyone. Moreover, the health benefits of physical
activity far outweigh the risks.

Still, people may hesitate to become physically active because of
concern they'll get hurt. For these people, there is even more good news:
They can take steps that are proven to reduce their risk of injury and adverse
events.

The Guidelines in this chapter provide advice to help people do
physical activity safely. Most advice applies to people of all ages. Specific
guidance for particular age groups and people with certain conditions is also
provided.

Explaining the Guidelines

Physical Activity Is Safe for Almost Everyone

Most people are not likely to be injured when doing moderate-intensity
activities in amounts that meet the Physical Activity Guidelines.
However, injuries and other adverse events do sometimes happen. The most common
problems are musculoskeletal injuries. Even so, studies show that only one such
injury occurs for every 1,000 hours of walking for exercise, and fewer than
four injuries occur for every 1,000 hours of running.

Both physical fitness and total amount of physical activity affect risk
of musculoskeletal injuries. People who are physically fit have a lower risk of
injury than people who are not. People who do more activity generally have a
higher risk of injury than people who do less activity. So what should people
do if they want to be active and safe? The best strategies are to:

Be regularly physically active to increase physical fitness; and

Follow the other guidance in this chapter (especially increasing
physical activity gradually over time) to minimize the injury risk from doing
medium to high amounts of activity.

Following these strategies may reduce overall injury risk.
Active people are more likely to have an activity related injury than inactive
people. But they appear less likely to have non-activity-related injuries, such
as work-related injuries or injuries that occur around the home or from motor
vehicle crashes.

Key Guidelines for Safe Physical Activity

To do physical activity safely and reduce risk of injuries and other
adverse events, people should:

Understand the risks and yet be confident that physical activity
is safe for almost everyone.

Choose to do types of physical activity that are appropriate for
their current fitness level and health goals, because some activities are safer
than others.

Increase physical activity gradually over time whenever more
activity is necessary to meet guidelines or health goals. Inactive people
should "start low and go slow" by gradually increasing how often and
how long activities are done.

Protect themselves by using appropriate gear and sports equipment,
looking for safe environments, following rules and policies, and making
sensible choices about when, where, and how to be active.

Be under the care of a health-care provider if they have chronic
conditions or symptoms. People with chronic conditions and symptoms should
consult their health-care provider about the types and amounts of activity
appropriate for them.

Choose Appropriate Types and Amounts of Activity

People can reduce their risk of injury by choosing appropriate types of
activity. As the table shows, the safest activities are moderate intensity and
low impact, and don't involve purposeful collision or contact.

Walking for exercise, gardening or yard work, bicycling or exercise
cycling, dancing, swimming, and golf are activities with the lowest injury
rates. In the amounts commonly done by adults, walking (a
moderate–intensity and low-impact activity) has a third or less of the
injury risk of running (a vigorous-intensity and higher impact activity).

The risk of injury for a type of physical activity can also differ
according to the purpose of the activity. For example, recreational bicycling
or bicycling for transportation leads to fewer injuries than training for and
competing in bicycle races.

People who have had a past injury are at risk of injuring that body
part again. The risk of injury can be reduced by performing appropriate amounts
of activity and setting appropriate personal goals. Performing a variety of
different physical activities may also reduce the risk of overuse injury.

The risk of injury to bones, muscles, and joints is directly related
to the gap between a person's usual level of activity and a new level of
activity.

The Continuum of Injury Risk Associated With Different Types of
Activity

Injury Risk
Level
(Risk Level from lower
to higher)

Activity Type

Examples

Lowest Risk

Commuting

Walking, bicycling

Lower Risk

Lifestyle

Home repair, gardening/yard work

Medium Risk

Recreation/sports
No contact

Walking for exercise, golf, dancing, swimming, running,
tennis

Higher Risk

Recreation/sports
Limited contact

Bicycling, aerobics, skiing, volleyball, baseball,
softball

Highest Risk

Recreation/sports
Collision/contact

Football, hockey, soccer, basketball

Note: The same activity done for different
purposes and with different frequency, intensity, and duration leads to
different injury rates. Competitive activities tend to have higher injury rates
than non-competitive activities, likely due to different degrees of intensity
of participation.

Increase Physical Activity Gradually Over Time

Scientific studies indicate that the risk of injury to bones, muscles,
and joints is directly related to the gap between a person's usual level
of activity and a new level of activity. The size of this gap is called the
amount of overload. Creating a small overload and waiting for the body to adapt
and recover reduces the risk of injury. When amounts of physical activity need
to be increased to meet the Guidelines or personal goals, physical activity
should be increased gradually over time, no matter what the person's
current level of physical activity.

Scientists have not established a standard for how to gradually
increase physical activity over time. The following recommendations give
general guidance for inactive people and those with low levels of physical
activity on how to increase physical activity:

Use relative intensity (intensity of the activity relative to a
person's fitness) to guide the level of effort for aerobic activity.

Generally start with relatively moderate-intensity aerobic activity.
Avoid relatively vigorous-intensity activity, such as shoveling snow or
running. Adults with a low level of fitness may need to start with light
activity, or a mix of light- to moderate-intensity activity.

First, increase the number of minutes per session (duration), and the
number of days per week (frequency) of moderate-intensity activity. Later, if
desired, increase the intensity.

Pay attention to the relative size of the increase in physical
activity each week, as this is related to injury risk. For example, a 20-minute
increase each week is safer for a person who does 200 minutes a week of walking
(a 10 percent increase), than for a person who does 40 minutes a week (a 50
percent increase).

The available scientific evidence suggests that adding a small and
comfortable amount of light- to moderate–intensity activity, such as 5 to
15 minutes of walking per session, 2 to 3 times a week, to one's usual
activities has a low risk of musculoskeletal injury and no known risk of severe
cardiac events. Because this range is rather wide, people should consider three
factors in individualizing their rate of increase: age, level of fitness, and
prior experience.

Age
The amount of time required to adapt to a new
level of activity probably depends on age. Youth and young adults probably can
safely increase activity by small amounts every week or 2. Older adults appear
to require more time to adapt to a new level of activity, in the range of 2 to
4 weeks.

Level of Fitness
Less fit adults are at higher risk
of injury when doing a given amount of activity, compared to fitter adults.
Slower rates of increase over time may reduce injury risk. This guidance
applies to overweight and obese adults, as they are commonly less physically
fit.

Prior Experience
People can use their experience to
learn to increase physical activity over time in ways that minimize the risk of
overuse injury. Generally, if an overuse injury occurred in the past with a
certain rate of progression, a person should increase activity more slowly the
next time.

Take Appropriate Precautions

Taking appropriate precautions means using the right gear and equipment,
choosing safe environments in which to be active, following rules and policies,
and making sensible choices about how, when, and where to be active.

Use Protective Gear and Appropriate Equipment
Using
personal protective gear can reduce the frequency of injury. Personal
protective gear is something worn by a person to protect a specific body part.
Examples include helmets, eyewear and goggles, shin guards, elbow and knee
pads, and mouth guards.

Using appropriate sports equipment can also reduce risk of injury.
Sports equipment refers to sport or activity-specific tools, such as balls,
bats, sticks, and shoes.

For More Information

See Appendix 2 for a resource chart that provides selected examples of
injury prevention strategies for common physical activities.

For the most benefit, protective equipment and gear should be:

The right equipment for the activity;

Appropriately fitted;

Appropriately maintained; and

Used consistently and correctly.

Be Active in Safe Environments
People can reduce
their injury risks by paying attention to the places they choose to be active.
To help themselves stay safe, people can look for:

Physical separation from motor vehicles, such as sidewalks, walking
paths, or bike lanes;

Neighborhoods with traffic-calming measures that slow down traffic;

Places to be active that are well-lighted, where other people are
present, and that are well-maintained (no litter, broken windows);

Shock-absorbing surfaces on playgrounds;

Well-maintained playing fields and courts without holes or
obstacles;

Breakaway bases at baseball and softball fields; and

Padded and anchored goals and goal posts at soccer and football
fields.

Follow Rules and Policies That Promote Safety
Rules, policies, legislation, and laws are potentially the most effective and
wide-reaching way to reduce activity-related injuries. To get the benefit,
individuals should look for and follow these rules, policies, and laws. For
example, policies that promote the use of bicycle helmets reduce the risk of
head injury among cyclists. Rules against diving into shallow water at swimming
pools prevent head and neck injuries.

Make Sensible Choices About How, When, and Where To Be
Active
A person's choices can obviously influence the risk of
adverse events. By making sensible choices, injuries and adverse events can be
prevented. Consider weather conditions, such as extremes of heat and cold. For
example, during very hot and humid weather, people lessen the chances of
dehydration and heat stress by:

Exercising in the cool of early morning as opposed to mid-day heat;

Switching to indoor activities (playing basketball in the gym rather
than on the playground);

Changing the type of activity (swimming rather than playing soccer);

Lowering the intensity of activity (walking rather than running); and

Paying close attention to rest, shade, drinking enough fluids, and
other ways to minimize effects of heat.

Inactive people who gradually progress over time to relatively
moderate-intensity activity have no known risk of sudden cardiac events, and
very low risk of bone, muscle, or joint injuries.

Exposure to air pollution is associated with several adverse health
outcomes, including asthma attacks and abnormal heart rhythms. People who can
modify the location or time of exercise may wish to reduce these risks by
exercising away from heavy traffic and industrial sites, especially during rush
hour or times when pollution is known to be high. However, current evidence
indicates that the benefits of being active, even in polluted air, outweigh the
risk of being inactive.

Advice From Health-Care Providers

The protective value of a medical consultation for persons with or
without chronic diseases who are interested in increasing their physical
activity level is not established. People without diagnosed chronic conditions
(such as diabetes, heart disease, or osteoarthritis) and who do not have
symptoms (such as chest pain or pressure, dizziness, or joint pain) do not need
to consult a health-care provider about physical activity.

Inactive people who gradually progress over time to relatively
moderate-intensity activity have no known risk of sudden cardiac events, and
very low risk of bone, muscle, or joint injuries. A person who is habitually
active with moderate-intensity activity can gradually increase to vigorous
intensity without needing to consult a health-care provider. People who develop
new symptoms when increasing their levels of activity should consult a
health-care provider.

For More Information

Health-care providers can provide useful personalized advice on how to
reduce risk of injuries. For people who wish to seek the advice of a
health-care provider, it is particularly appropriate to do so when
contemplating vigorous-intensity activity, because the risks of this activity
are higher than the risks of moderate-intensity activity.

The choice of appropriate types and amounts of physical activity can be
affected by chronic conditions. People with symptoms or known chronic
conditions should be under the regular care of a health-care provider. In
consultation with their provider, they can develop a physical activity plan
that is appropriate for them. People with chronic conditions typically find
that moderate-intensity activity is safe and beneficial. However, they may need
to take special precautions. For example, people with diabetes need to pay
special attention to blood sugar control and proper footwear during activity.

Women who are pregnant and those who've recently had a baby should
be under the regular care of a health-care provider. Moderate-intensity
physical activity is generally safe for women with uncomplicated pregnancies,
but women should talk with their provider about how to adjust the amounts and
types of activity while they are pregnant and right after the baby's
birth.

For More Information

Doing activities that involve lying on their back after the first
trimester of pregnancy; and

Doing activities with high risk of falling or abdominal trauma,
including contact or collision sports, such as horseback riding, soccer,
basketball, and downhill skiing.

Gradually Increasing Physical Activity Over Time: Real-Life
Examples

Here are two examples that show how people at different ages, levels of
fitness, and levels of experience can safely become more active over time.

Bill: A Man Who Has Been Inactive for Many Years

Bill wants to work his way up to the equivalent of 180 to 210 minutes (3
hours to 3 hours and 30 minutes) of walking a week. On weekdays he has time for
up to 45 minutes of walking, and he plans to do something physically active
each weekend. He decides to start with walking because it is moderate intensity
and has a low risk of injury.

The first week, Bill starts at a low level. He walks 10 minutes a
day 3 days a week. Sometimes he divides the 10 minutes a day into two sessions.
He prefers to alternate rest days and active days. (Total = 30 minutes a week.)

Between weeks 3 and 8, Bill increases duration by adding 5 minutes a
day and continues walking on 3 non-consecutive days each week. The weekly
increase is 15 minutes. (Week 3 total = 45 minutes. Week 8 total = 120 minutes
or 2 hours.)

In week 9, Bill adds another day of moderate intensity activity on
the weekend, and starts doing a variety of activities, including biking,
hiking, and an aerobics class. Gradually increasing the minutes of activity, by
week 12 he is doing 60 minutes or more of moderate-intensity activity on the
weekend. Reaching his goal: Over 3 months, Bill has increased to a total of 180
moderate-intensity minutes a week.

Kim: An Active Woman

Kim currently does 150 minutes (2 hours and 30 minutes) a week of
moderate-intensity activity. She wants to work up to at least the equivalent of
300 minutes (5 hours) of moderate-intensity activity a week. She also wants to
shift some of that moderate intensity activity to vigorous-intensity activity.
Her current 150 minutes a week includes:

Thirty minutes of mowing the grass 1 day a week;

Thirty minutes of brisk walking 4 days a week; and

Fifteen minutes of muscle-strengthening exercises 2 days a week.

Increasing frequency and duration:

Over a month, Kim adds walking on another weekday, and she gradually
adds 15 minutes of moderate-intensity activity on each of the 5 walking days
each week. This provides an additional 105 minutes (1 hour and 45 minutes) of
moderate–intensity activity.

Increasing intensity:

Over the next month, Kim decides to replace some walking with
jogging. Instead of walking 45 minutes, she walks for 30 minutes and jogs for
15 minutes on each weekday, providing the equivalent of 300 minutes a week of
moderate-intensity physical activity from her walking and jogging.

Reaching her goal: After these increases, Kim is doing
a total of 180 minutes of moderate-intensity activity each week (walking and
mowing) and also doing 75 minutes (1 hour and 15 minutes) of
vigorous–intensity jogging. One minute of vigorous-intensity activity is
about the same as 2 minutes of moderate intensity activity, so she is now doing
the equivalent of 330 moderate-intensity minutes (5 hours and 30 minutes) a
week. She has more than met her goal.